A detailed study of the results of chronic cerebellar stimulation in 5 patients subject to severe intractable seizures of multifocal nature has been finished with a 20-24 month follow-up. Despite unanimous approval of the procedure by the patients and their families, regular documentation of the seizure frequency on the ward failed to show any improvement in the seizure frequency over the postoperative period or any relationship between the periods without and with cerebellar stimulation which was applied both in the unblinded and double blind modes. However, studies of the CSF concentrations of both norepinephrine and GABA showed changes related to the stimulation with a rise of the former and a fall of the latter (GABA). Although both of these substances have some suppressive effect upon seizure states (although numerous discrepancies appear in the literature) the possible elevation of mood attending a rise in CSF norepinephrine may be the most potent factor. None of the families reported loss of seizures with stimulation but all found the patients more alert, less irritable and generally easier to get on with. A direct relationship between the CSF levels of norepinephrine and depression (fall of norepinephrine with increasing depression and vice versa) is documented in the literature. BIBLIOGRAPHIC REFERENCES: Wood, J.H., Ziegler, M.G., Lake, C.R., Shoulson, I., Brooks, R.R. and Van Buren, J.M.: Cerebrospinal Fluid Norepinephrine Reductions in Man after Degeneration and Electrical Stimulation of the Caudate Nucleus. Ann. Neruol. 1: 94-99, 1977. Wood, J.H., Lake, C.R., Ziegler, M.G., and Van Buren, J.M.: Neurophysiological and neurochemical alterations during electrical stimulation of human caudate nucleus. J. Neurosurg. 46: 361-368, 1977.